


The Calculus of Infinitesimals

by ilovehowyouletmefall



Category: Buffy the Vampire Slayer (TV)
Genre: F/M, Fluff and Smut, Light Dom/sub, Oral Sex, Plot What Plot/Porn Without Plot, Season/Series 02
Language: English
Status: Completed
Published: 2020-09-18
Updated: 2020-09-18
Packaged: 2021-03-07 17:54:42
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,116
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26521744
Author URL: https://archiveofourown.org/users/ilovehowyouletmefall/pseuds/ilovehowyouletmefall
Summary: Jenny tests Rupert's limits, and challenges some of her own.
Relationships: Jenny Calendar/Rupert Giles
Comments: 5
Kudos: 39





	The Calculus of Infinitesimals

**Author's Note:**

> This started out as a Tumblr post about head canons, that ended up far too detailed for a Tumblr post. And I thought there's always room in the world for more Giles/Jenny PWP.

After Eyghon, Jenny doesn’t think there’s anything else to learn about Rupert. She finds out she’s wrong the first time they have sex. Not only is Rupert far from the shy and blushing suitor she had made him out to be, he also turns out to be quite... versatile. He can turn from tender romantic to ferocious lover on a dime if Jenny gives any indication that that’s what she wants. 

Jenny soon figures out that the one consistent thing about Rupert is that he’s very, very good at following instructions. If she says something suggestive, or flirty, or filthy to him, he takes it as a challenge to fulfill her wishes, seemingly as a point of pride. To see how far she can take it - because if Jenny isn’t testing Rupert’s limits, then what’s even the point - she starts to pass him notes over the course of the school day. If she sees him in the hallway, or at a staff meeting, she hands him a folded piece of paper, and then watches as he reads her very clear and descriptive step-by-step instructions. His pupils dilate, and colour rises in his cheeks, as he otherwise remains composed. Then he folds the note and puts it in his jacket pocket, coughs slightly and acts as if nothing had happened. But later, he always follows Jenny’s instructions to a tee. 

There’s something about sleeping with him that gives Jenny a heady rush, something addicting. It seems like Rupert will do anything she asks. So in her relentless pursuit to push every one of his buttons, she decides to try to find an exception. 

(Of course, there’s also the fact that if she’s thinking about her relationship with Rupert in terms of sex, and how wildly good the sex is, then she isn’t thinking about how she decided to go back to him even after he had hurt her, or how much trust she’s placing in him, or how the thought of saying “I love you” is beginning to cross her mind with alarming frequency.)

* * *

Jenny visits Giles in his office one day during lunch. He smiles broadly when he sees her. She locks his office door, and he rises to greet her with a kiss. They had made out in his office a couple of times before, but had never gone any further. This time, Jenny has other ideas.

She rests her hands on his chest and pushes until his back hits the wall. The kiss deepens, and her hands slide down his torso, and between his legs.

Giles breaks off the kiss with a sharp intake of breath. 

“Jenny, we’re at work...” he says with a hint of amusement.

“Yeah. Does that turn you on?” Jenny counters. 

She undoes his belt and his pants, and it dawns on Giles that Jenny is not just teasing.

“W-well... um...”

She drops to her knees.

“Jenny...” he gasps as she takes him in her mouth.

“You’re gonna need to be quieter than that,” she says, and circles her tongue around the head of his cock. 

He shuts his eyes and suppresses a moan. She goes back to work. 

After about five minutes of watching Giles sigh and shudder under her attentions, Jenny feels his hands caressing her hair. Based on the previous times that she’s gone down on him, she knows that it means he’s about to pull her off of him, to make sure that she comes at least once before he gets off. While she very much appreciates the thought, the pattern is getting to be predictable, and Jenny decides that she’s not going to let Rupert have his way. She’s there to make him squirm, and he’s not getting out of it that easy. 

“Rupert, stay still.”

“What?” he mutters breathlessly.

Her voice is low and commanding. “Don’t move until I’m done.”

And she keeps going. His hands hover over her head, and shake, and clench into fists, his nails digging into his palms. Giles curses under his breath, which soon devolves into begging. He whispers through clenched teeth, to please let him go down on her, please let him make love to her, please let him fuck her till she can’t see straight. _Please_.

Jenny doesn’t ignore his pleas. It’s just that she’s enjoying making Rupert beg too much to give him what he wants. 

He comes, biting his tongue and swallowing down a cry. 

Jenny gets to her feet. She stands on her toes so that her lips brush against his. 

“Well done,” she says.

She pecks him gently on the lips, once, twice. He moves to hold her close, but she steps away before he can.

The bell rings. “See you after school,” she says. 

Feeling Rupert’s eyes on her, as well as feeling very proud of herself, she walks out the door.

* * *

When Jenny strides through the library doors after class, Giles is explaining to Buffy that he needs to cancel training so that he can look up a potential prophesy in one his books at home. 

Of course, Buffy doesn’t seem to mind at all. Jenny is disappointed, she was hoping that she and Rupert could spend their time on something other than research that night. But part of dating a Watcher is resigning herself to the fact that sometimes saving lives has to take priority.

“Ah, Jenny,” he says when he sees her. “Good, I’ll need your help.”

“Can it wait an hour?” she asks. “I just came by to let you know that I have a few things to finish off in the lab.”

“This is more important,” he says definitively, already gathering his things and heading towards the door. “See you tomorrow, Buffy.”

“Okay, should I check in after patrol?” Buffy asks.

“I don’t think that’s necessary, you can tell me about it tomorrow,” Giles replies, taking Jenny by the arm and guiding her out of the library, leaving a baffled Buffy behind. 

Once they’re in Giles’ car, Jenny asks, “So what’s the emergency?” 

Giles leans over and kisses her, fiercely. It takes her a second to adjust to what’s happening, his hand cupping her face, his mouth on hers, pressing and hungry. When he pulls away, he’s breathing heavily, his gaze flitting from her eyes to her lips. 

“Oh,” she breathes.

Giles waits for her to say something else. When she doesn’t, the corner of his mouth curls into a gentle smile. He turns and starts the car. 

Jenny’s heart is racing, and a sense of anticipation is pinging around her insides. She thinks she ought to tease Rupert, or say something to rile him up. Isn’t that what Jenny Calendar would do in this situation? Try to knock him off balance, the same way he took her off guard with that kiss? But she doesn’t want to. Jenny feels like she’s unlocked a door, and instead of being scared of what’s on the other side, she wants to see where it leads.

As soon as they’re through the door to Giles’ apartment, he’s kissing her. He presses her body close to his, and trails his lips down her neck and shoulder, and then his mouth is on hers again. Jenny meets his kiss with just as much feverish passion. She runs her fingers through his hair, and Giles quickly throws off his jacket, waistcoat, and tie, breaking the kiss just long enough to drop his glasses on his desk. Then his hands are on her body again, and she sighs at his touch. He caresses her breasts, her stomach, her rear. 

Suddenly, he lifts her up. Jenny reflexively wraps her legs around his waist before she realizes what’s happening. All at once, she feels helpless, literally ungrounded. Unexpectedly, it doesn’t feel bad. She thinks she trusts Rupert, but quickly decides that she doesn’t want to think about what that means, so she kisses him again. 

Giles carries her to the foot of the stairs, and pins her against the wall. He peels off her top, and Jenny is very glad that she did not wear a bra that day. He turns his attention to her newly exposed breasts, squeezing and caressing with his hands, teasing her nipples with his tongue and teeth. Jenny tangles her fingers in his hair and lets the sensation of mounting pleasure wash over her. 

Giles stops, and lowers her legs from around his waist. Jenny is about to whine in disappointment, but then he takes her hand to lead her up the stairs to the bed. 

* * *

Once they’re in the loft, Jenny is quickly in Giles’ arms again. Then she’s on the bed, then she’s naked, then she’s watching him undress, his eyes never leaving her form. She’s on her back, and Giles is kissing his way down her body, grazing his teeth over her breasts, sucking marks into her abdomen and around her hip bones. She feels his lips on her clit, and it’s like she’s back on solid ground, safe and sure. Jenny smiles broadly, and arches her back against the bed, moaning encouragement to Rupert. He sucks her clit, teases it with his tongue, and slides a finger inside her. He does everything exactly right to bring her to climax, warm and glowing. 

And then Giles doesn’t stop. He has two fingers inside her, curling to hit her g-spot, and he presses against her clit with his tongue. Jenny is already shaking and breathless, and he keeps pushing her further. A part of her wants to tell him to stop, not because she’s not enjoying herself, but just for the sake of telling him to do something. Instead she bites her lip, and gives herself over to the feeling, gives herself over to him. He doesn’t stop until she’s a jittering mess on the bed, unable to tell one sensation from another. 

* * *

Giles is painfully hard by the time he’s done going down on Jenny. He stands, drags her hips to the edge of the bed, wraps her legs around his waist, and slides inside her. He takes his time, slowly thrusting into her, thumbing at her clit, enjoying the sight of Jenny quivering and arching her back with every move he makes. Her dark hair is spread across his sheets, her eyelashes flutter against her cheeks, her lips are flushed and murmuring incoherently. Her skin glistens with sweat, and her chest heaves with every breath. She’s beautiful, and he can’t help thinking that he wants to spend forever making her feel this way. He leans over and kisses her, kneeling on the bed now, and picks up his pace. She claws at his back and his name tumbles over her lips again and again, like a she’s chanting a spell. She comes again, shouting the names of dead gods, and he can’t last any longer. Giles comes so hard his vision goes hazy at the edges, and he feels dizzy for a moment. He collapses on the bed next to Jenny, kisses her face, whispers words of adoration in her ear. He loves her, and is about to say so, but then she kisses him. 

* * *

Jenny wakes up a few hours later, feeling relaxed and happy. Giles isn’t next to her, but she can hear him in the kitchen downstairs. A glance at the clock tells her it’s only 8pm.

Jenny finds a bathrobe and puts it on. When she gets to the bottom of the stairs, she sees Giles, in an old grey t-shirt an pajama pants, cooking pasta and singing softly to himself. _I love him_ , she thinks, briefly, before tossing the thought aside. Instead of saying anything, Jenny goes into the kitchen, walks up behind Giles as he works at the stove, and gently wraps her arms around his waist, resting her cheek against his back. 

“Hi,” she says.

Doing his best not to break the circle of her embrace, Giles turns around and kisses her hello. 

“Are you hungry?” he asks.

“Starving,” she answers. Jenny is fairly certain that there’s a dopey smile on her face, but she doesn’t really care. 

They eat in comfortable silence, sitting at the kitchen counter. Jenny’s not sure that she could string words into a full sentence if she tried. Besides, she’s genuinely hungry, and Giles is a good cook. 

Jenny notices that Giles can’t keep his eyes off her, which is understandable. But he’s also not so much smiling as he is smirking, and generally looking very pleased with himself. She would have to do something about that.

Jenny puts her empty plate aside, stands up, and extends her hand to Giles. 

“Rupert, come back to bed,” she says.

He takes her hand and follows her. 


End file.
